Web Lifter/Stabilizer And Method

ABSTRACT

Web lifter and/or stabilizer and method of lifting and/or stabilizing a travelling web and for coating a web. The device creates a web hold down force via a negative pressure slot at its exit side, which draws the web down against the surface on the entry side. The device can be actuated to move the web relative to a slot die coater off the die lips and stop the application of slurry to the web, thereby creating uncoated regions on the web surface. The device can then be actuated to move the web back into contact with the coater to start the application of slurry to the web, thereby creating coated regions on the web surface. Web lifting can be accomplished by rotating the device in first and second directions to lift the web off of the slot die coater and return the web back into contact with the coater.

This application is a divisional of U.S. patent application Ser. No.14/122,753 filed Nov. 27, 2013, the disclosure of which is incorporatedherein by reference. U.S. patent application Ser. No. 14/122,753 is a371 of International Application No. PCT/US2012/040667 filed Jun. 4,2012, which claims priority of U.S. Provisional Application Ser. No.61/493,046 filed Jun. 3, 2011, the disclosures of which are incorporatedherein by reference.

This application is related to co-pending International Application No.PCT/US2012/033508 filed on Apr. 13, 2012, the disclosure of which isincorporated herein by reference.

BACKGROUND

The embodiments disclosed herein relate to an apparatus and method forlifting and/or stabilizing a web, particularly applicable inintermittent coating operations, such as those used in manufacturingbatteries, where the substrate is coated in a series of discretepatches. Further embodiments relate to a method for controlling saidapparatus to provide precise control of length and thickness profile ofsaid discrete coating patches.

There are various applications in which it is desirable to deposit acoating onto at least a portion of a sheet of material. For example, insome embodiments, the electrodes of batteries are produced by applying alayer or coating to a sheet, and then cutting the sheet into portions ofa suitable dimension. Of particular importance is that the layer beapplied at a uniform thickness. In some embodiments, the layer orcoating is not applied to the sheet in the region where the sheet willsubsequently be cut.

In the manufacture of lithium ion batteries and the like, there is acoating process that applies anode slurry to a conductive substrate(e.g., copper foil) and another coating process that applies cathodeslurry to a conductive substrate (e.g., aluminum foil). In these twocoating processes, there are two different methods of coating:discontinuous, also referred to as skip or patch coating, and continuouscoating. In the practice of either method, the coating material may beapplied to the continuously moving substrate in the form of one or morelanes running parallel to the travel direction of said continuouslymoving substrate. One method of coating known to those skilled in theart has a backing roller on which the moving substrate is conveyed in anarcuate path as it is supported and is positioned precisely by thesurface of said backing roller. In some cases, it is not convenient oreven possible to allow the web to contact a backing roller, such as inthe case of coating both sides of the web with a wet material beforeboth said applied coatings are dried. In the practice of the embodimentsdisclosed herein, the web is conveyed in a free span between web supportelements. Said web support elements could be one or more idler rollers,vacuum tables or air flotation bars which position and guide the path ofweb travel in a straight path.

An example of such a prior art system is shown in FIG. 15, whereinslurry is applied to the moving substrate web 310 in a free span betweenweb support elements 315 and 320 via a slot die coater 70 attached to apumping station. The coating is typically held in a tank or reservoir30. The coating is drawn from the reservoir 30, through conduit 31 bypump 40. The coating is then passed through conduit 32 by the action ofthe pump 40. In the case where coating is not being applied to the sheet10, bypass valve 63 is open while supply valve 60 is closed. This allowsthe coating that is pumped through conduit 32 to pass through conduit 33and back to reservoir 30. In the case where coating is being applied tothe sheet 10, the bypass valve 63 is closed, while supply valve 60 isopened. This permits the flow of coating through conduit 62 to thenozzle 70, and onto the sheet 10. While the supply valve 60 is open, thecoating is discharged by the nozzle 70. However, when the supply valve60 is closed, the pressure needed to propel the coating through thenozzle 70 is eliminated. In some cases, this causes excess coatingmaterial to remain in the cavity, or manifold 71, and the lips 72 of thenozzle. When the supply valve is next opened, this excess material maycause an uneven application of coating to the sheet 10. FIG. 16 shows anexample of the result of this phenomenon on the coated patch thickness.Coated patch 500 is shown as a cross-section profile of thickness “x”applied to web 10. As the sheet moves toward the left, starting profile520 is thicker than the rest of the coating 500. This excess material510 is due to the residual coating material that remained in the nozzle70 after the supply valve 60 was closed. In this figure, the endingprofile 525 is shown to be uneven, as the valves may be transitioningwhile the coating is still being applied. Such an uneven coating may beunacceptable.

Therefore, to prevent this uneven application, a fluid suction mechanism80′ may be used, as shown in FIG. 15. This fluid suction mechanism isused to draw the excess coating that is left in the manifold 71 or onthe lips 72 away from the nozzle 70. In operation, pump 40 draws coatingmaterial from reservoir 30. The coating material passes through conduits31, 32 and is directed toward the nozzle 70, where it is discharged ontothe sheet 10 as the sheet is drawn past roller 15. To stop the flow ofcoating onto the sheet 10, the bypass valve 63 is opened and the supplyvalve 60 is closed, thereby diverting the coating material throughconduit 33 and back into the reservoir 30. To remove excessive coatingmaterial that may be present in the manifold 71 or on the lips 72 of thenozzle 70, valve 85 is opened to suction source 80 so that fluid isdrawn by vacuum through conduit 86 which is in fluid communication withdie manifold 71. The suction source 80 is typically comprised of avacuum reservoir tank in communication with a suction pump to create adraw of fluid from die cavity 71 when valve 85 is opened. Coating fluidmaterial is collected in said reservoir tank and periodically removedfor reuse or, more often, discarded as waste material.

To restart the flow of coating onto the sheet 10, valve 85 is closed toremove the vacuum drawing fluid through conduit 86. Bypass valve 63 isclosed while supply valve 60 is opened.

In the practice of free span coating, the planarity of the web is ofsignificant importance in applying a uniform thickness of coating fluidto the web in the direction of web travel and in the cross-webdirection. As the foil web approaches the slot die coater, the web mustremain flat as it travels over the slot die coater, but due to a baggyweb or tension corrugation in the thin foil, the web will tend to liftoff the slot die coater or otherwise deviate from the desired path oftravel resulting in a non-uniform gap between the fluid discharge lipsof said slot die coater and the web surface to be coated. Without auniform gap to the slot die coater discharge lips, the coating processcreates defects in the coated web, such as non-uniform thickness ofapplied coating, ridges or streaks.

It therefore would be desirable to provide an apparatus and method forstabilizing the web in the free span to help provide defect-freecoatings. It would also be desirable to utilize the same apparatus tomove the web relative to the slot die coater to an off coat position inorder to create the uncoated portion of the web, and return the web toan on coat position in order to create the coated portion of the web.This web movement would be especially useful in discontinuous coating ofpatches in precise position spacing and uniformity to precisely controlthe lengths and thickness profile of the coated and non-coated patchesalong the direction of travel. It would further be desirable to providea device for guiding and flattening a running web.

SUMMARY

Problems of the prior art have been overcome by the embodimentsdisclosed herein, which relate to a web lifter and/or stabilizer andmethod of lifting and/or stabilizing a travelling web of material. Inaccordance with certain embodiments, the device creates a web hold downforce via a negative pressure slot at the exit side of the device. Thisnegative pressure slot draws the web down against the surface on theentry side of the device, which in certain embodiments is a highlypolished flat metal surface. The need for a precision backing roll iseliminated.

In accordance with certain embodiments, the device can be actuated tomove the web relative to a slot die coater used in a skip coating orintermittent coating operation, to move the web off the die lips andstop the application of coating (e.g., slurry) to the web, therebycreating uncoated regions on the web surface. The device can then beactuated to move the web back into contact with the slot die coater tostart the application of coating to the web, thereby creating coatedregions on the web surface. In certain embodiments, the web lifting isaccomplished by rotating the device in a first direction to lift the weboff of the slot die coater and rotating the device back in an oppositedirection to return the web back into contact with the slot die coater.A controller can be used to actuate the device.

In accordance with certain embodiments, the device can be used to guideand flatten a travelling web in a web path. Such a device need to berotatable when lifting the web of a slot die coater is not necessary.

In certain of its method aspects, in certain embodiments a coater forintermittently applying a coating to a web is provided, and the weblifter and/or stabilizer is provided upstream of the coater, in thedirection opposite of web travel, in a first position. Negative pressureis applied to the web lifter and/or stabilizer body, causing air toenter the air entry slot and flow to the vacuum chamber. When a gap orskip in coating is desired on the web surface, the web lifter body isrotated from the first position in a direction toward the web to deflectthe web away from the coater (e.g., away from the coater lips) to form acoating gap (e.g., an area devoid of coating) on the web. The body isthen rotated back to the first position once the desired gap is formed,and negative pressure is maintained during both direction rotations.

In a preferred embodiment, a computer-controlled fluid delivery systemprovides precise control of the actuation of the valves and movement ofthe web lifter/stabilizer to create a plurality of coating profiles. Thesystem includes a controller, which is used to actuate the valves tobegin and terminate the flow of material onto the sheet through a slotdie nozzle. In addition, the controller may displace the web from itson-coat position to an off-coat position away from the sheet by movementof the web lifter/stabilizer. In some embodiments, a fluid displacementmechanism is used to temporarily withdraw coating fluid from the slotdie lips during the off-coat cycle and return the fluid to the lipsduring the next on-coat cycle. In two-side coating embodiments, thecontroller is also able to control the start and end locations of thecoated patches on the opposite side of the sheet. Registration of thecoating can be programmed to be in exact alignment, or advanced ordelayed by a specific amount. In addition, the present system is aposition based system, thereby being capable of automaticallyaccommodating changes in line speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a portion of the web lifter andstabilizer in accordance with certain embodiments;

FIG. 1B is a cross-sectional view of a portion of the web lifter andstabilizer in accordance with an alternative embodiments;

FIG. 2 is a front view of a gusset for the web lifter and stabilizer inaccordance with certain embodiments;

FIG. 3 is a cross-sectional view of a portion of the web lifter andstabilizer in accordance with certain embodiments;

FIG. 4 is a top view of the portion of FIG. 1A;

FIG. 4A is a top view of the portion of FIG. 1B in accordance with analternative embodiment;

FIG. 5 is a bottom view of a portion of the web lifter stabilizer inaccordance with certain embodiments;

FIG. 6 is a cross-sectional view of the portion of FIG. 5;

FIG. 7 is a side view of a vacuum reservoir in accordance with certainembodiments;

FIG. 8 is a top view of the vacuum reservoir in accordance with certainembodiments;

FIG. 9 is a top view of the assembly of the web lifter and stabilizerrotation device in accordance with certain embodiments;

FIG. 10 is a top view of the complete assembly of web lifter andstabilizer in accordance with certain embodiments;

FIG. 11 is a first side view of the web lifter and stabilizer assemblyin accordance with certain embodiments;

FIG. 12 is a second side view of the web lifter and stabilizer assemblyin accordance with certain embodiments;

FIGS. 13A and 13B are schematic diagrams showing the web lifter andstabilizer and a slot die coater in the on coat position and the offcoat position in accordance with certain embodiments;

FIGS. 14A and 14B are schematic diagrams showing the web lifter andstabilizer and a slot die coater in the on coat position and the offcoat position in accordance with certain alternative embodiments.

FIG. 15 shows an example of prior art practice in coating a web in freespan with a slot die nozzle;

FIG. 16 shows the profile of a coating applied to the sheet using thesystem of FIG. 15;

FIG. 17 shows a representative system in accordance with certainembodiments;

FIG. 18 shows a timing diagram used to produce the coating profile ofFIG. 16;

FIG. 19 shows a second profile of a coating that may be applied to asheet in accordance with certain embodiments;

FIG. 20 shows a timing diagram used to produce the coating profile ofFIG. 19;

FIG. 21 shows a third profile of a coating that may be applied to asheet in accordance with certain embodiments;

FIG. 22 shows a timing diagram used to produce the coating profile ofFIG. 21; and

FIG. 23 shows a representative embodiment of an optional fluiddisplacement mechanism.

DETAILED DESCRIPTION

Turning first to FIGS. 10-12, there is shown an exemplary embodiment ofa web lifter and stabilizer assembly 10 in accordance with certainembodiments. The assembly 10 includes mounting brackets 11, 11′, whichsupport a pair of oppositely located shaft stubs 12 via bearing mounts13, 13′, web lifter and stabilizer 15, and vacuum reservoir 16. The weblifter and stabilizer has a rotatable element 15 comprised of awing-shaped body 50 (FIG. 1) having a first portion defining a leadingedge of said apparatus when in operation, and a second portion defininga trailing edge when in operation, the first portion being spaced fromthe second portion so as to define a slot 25 between them for the entryof air upon the application of negative pressure to the body 50. Vacuumreservoir 16 is in fluid communication with the body 50 for receivingair entering the slot 25; the body being rotatable between a firstposition in which the web travels in an undeflected state, and a secondposition in which the web is deflected by the body 50 so as to travel ina deflected state. A driving force, such as a servomotor 17, is attachedto the shaft stubs 12 that are welded to each end of the body 50 torotate this body 50. A 3000 rpm motor has been found to be suitable,although the embodiments disclosed herein are not limited thereto. Forexample, an air cylinder activated by a solenoid-operated valve could bemechanically coupled to said shaft to move the lifter assembly betweenthe coat and off-coat positions. One of the shaft stubs 12 is attachedto the motor via a coupling 18. A bellows servo style coupling has beenfound to be suitable for this purpose, although the embodimentsdisclosed herein are not limited thereto. In certain embodiments, twoshaft stubs are provided and welded to the body with a space in betweenfor air from slot 25 to pass through apertures 24 a through 24 n intoreservoir 16.

In a preferred embodiment, the vacuum reservoir 16 and apertures 24 a to24 n are eliminated and the suction air flow path is alternatively madethrough one or more hollow shafts 12 a (FIGS. 1B and 4A) connected bysuitable means such as a flexible hose or rotary fitting (not shown) toa suction source. In this embodiment, the hollow shaft 12 a can replacethe solid shaft 12 and one or both ends of the assembly 50. The shaftscan be shaft stubs (rather than full length of the assembly) that do notextend all the way across the length of assembly 50. This allows the airto pass through the bulbous part of the wing assembly 50. In FIG. 4A(which corresponds to an end view shown in FIG. 1B) the hollow shaftstub 12A extends only partly into the assembly 50, as shown. Similarly,the non-hollow shaft stubs 12 in the embodiment of FIG. 4 (whichcorresponds to an end view shown in FIG. 1A) extend only partly into theassembly 50. In both embodiments 4 and 4A, the air enters the slot 25and is guided inside the wing assembly bounded by surfaces of the Jshaped member 20, the bent member 21, and the gussets 27 which close offeach end of the wing assembly in conjunction with the shaft stubs 12 or12A. In the embodiment of FIG. 4, the air then passes through apertures24 a-24 n as depicted in FIGS. 13A and 13B, and into vacuum reservoir16. In the embodiment of FIG. 4A having hollow shaft stubs 12A, theapertures in the J-shaped member 20 and the vacuum reservoir 16 areeliminated. The air flow path from slot 25 is again bounded by surfacesof the J shaped member 20 (devoid of apertures) and the bent member 21and guided to one or both ends of wing assembly 50 having at least onehollow shaft stub 12A connected to a suction source. The air passesthrough the hollow shaft stub or shaft stubs 12A into the suction source(not shown) as depicted in FIGS. 14A and 14B.

Turning now to FIGS. 1-6, there are shown details of the web lifter andstabilizer assembly 10 in accordance with certain embodiments. Forsimplicity, the vacuum reservoir 16 is not shown in these figures. Thebody 50 includes an elongated J-shaped member 20 coupled to elongatedbent member 21. Although two separate members are shown, those skilledin the art will appreciate that a single integral body 50 could beformed. As best seen in FIG. 4, elongated J-shaped member 20 is longerin the web width direction than bent member 21, since the web 100 isalways wider than the coated area (e.g., by at least 25 mm). Extendingthe J-shaped member out beyond the die lips of a slot die coater 200helps stabilize the uncoated edges of the web 100. If this were not inplace, the edges would crease and flip up and down as they traveled overthe die, creating coating defects at the edge of the coating. ElongatedJ-shaped member 20 includes a straight or flat portion 20A that contactsthe web when the device is in the on coat position, and defines theaforementioned leading edge. Preferably the surface of the portion 20Ais a smooth and highly polished (e.g., to a mirror finish) metalsurface. In certain embodiments, a low friction coating such as TEFLON®may be applied to surface of 20A. Anti-friction coatings may includeanti-wear elements such as ceramic beads to reduce friction and resistwear. Such coatings are available from Racine Flame Spray of Racine,Wis., USA, and other sources of plasma spray coatings. The surface mayalso be machined to a smooth surface. Elongated J-shaped member 20 alsoincludes a curved or U-shaped portion 20B, the U-shape having acurvature matching that of the shaft stubs 12 and a radius slightlylarger than the radius of the shaft stubs 12 so that the shaft stubs 12sit within the U-shape as seen in FIG. 1. As best seen in FIGS. 5 and 6,the U-shaped portion 20B of the elongated J-shaped member includes aplurality of spaced apertures 24 a-24 n along its length. In certainembodiments, the apertures 24 a-24 n are each 0.5 inches in diameter,and are positioned so that the center of each aperture is 30° from thelongitudinal centerline x (FIG. 6) of the J-shaped member 20. Theapertures 24 a-24 n are located between the spaced shaft stubs 12, andallow for fluid communication from the slot 25 to the vacuum reservoir,as discussed in greater detail below. Extending from the U-shapedportion 20B is straight portion 20C, which is shorter than straightportion 20A. In the embodiment shown, the U-shaped member 20B, theportion 20A and the straight portion 20C are a single, integral metalpiece.

FIGS. 1 and 3 also show the bent member 21, which in certain embodimentsincludes a short top portion 21A, which bends at a 22° angle to middleportion 21B, which in turn bends at a 30° angle to bottom portion 21C.In certain embodiments, the short top portion 21A has an overlappingbend to keep it straight/flat and to make it rounded so as to not ripthe web. In certain embodiments the top portion 21A may be fabricatedfrom a strip of machinable material and milled to a specified flatnessmatching the flatness of the die lips upon which the surface 21A restswhen in the on-coat position. Bottom portion 21C is coupled to portion20C of the elongated J-shaped member 20 such as by welding. The bentmember 21B includes a plurality of spaced punched slots 23, eachpreferably centrally located along the length of the bent member toreceive tabs 27A and 27B on gusset 27 (FIG. 2). When so coupled, themiddle portion 21B of bent member 21 cooperates with straight portion20A of elongated J-shaped member 20 to form a slot 25 (FIG. 1). Incertain embodiments, the slot 25 can be 0.16 inches wide. In certainembodiments, negative pressure is applied to the slot 25 in the range offrom 0.5 inches to 1.5 inches wc, depending on the tension in the web.In certain embodiments, the middle portion 21B is angled such that whenthe device is in operation and in the on coat position, the middleportion 21B is parallel or substantially parallel to the side of theslot die coater 200. The short top portion 21A defines theaforementioned trailing edge of the body 50.

A plurality of spaced gussets 27 (FIG. 2) are positioned in spacedrelation along the length of the device. Tab 27A of each gusset 27 isreceived in a respective slot 23 of bent member 21 and tack weldedthere. Tab 27B of each gusset 27 is received in a respective cutout atthe terminal end of portion 20C of elongated J-shaped member 20. Incertain embodiments, there are five spaced gussets positioned along thelength of the device. Each gusset 27 includes an arc-shaped bottomportion 26 configured to accommodate the shaft 12. The gussets help holdthe vacuum slot 25 gap/width and help in maintaining cross web surfaceflatness.

Turning now to FIGS. 7-12, there is shown vacuum reservoir 16. Incertain embodiments, the vacuum reservoir 16 includes an arc-shapedportion 36 that connects to the U-shaped portion 20B of the elongatedJ-shaped member 20, as can be seen in FIG. 11. This creates fluidcommunication between the slot 25 and the vacuum reservoir 16 so thatair entering the slot 25 passes through the plurality of holes 24 a-24 nin the U-shaped member and enters the vacuum reservoir, and thenultimately flows back to the fan inlet and is dumped to ambient.Preferably the radius of the arc-shaped portion matches the radius ofthe U-shaped portion to facilitate the connection. The arc-shapedportion 36 bends at its distal end to define an elongated portion 46that forms the remainder of the vacuum reservoir. An aperture 48 (FIG.8) is formed in a wall of the reservoir 16 to provide fluidcommunication to a vacuum source, such as a fan, through suitableducting and/or hosing. In certain embodiments, the negative pressure isdrawn from the backside of the reservoir 16 outside the web width forthe feed hose clearance, a 1″ we slot pressure difference is createdacross the length of the reservoir, with the side closest to the hoseconnection 48 being higher. To accommodate this, a perforated diverter39 can be placed in the reservoir as shown in FIG. 8 to even out thecross web pressures in the vacuum slot. The size of the diverter willdepend in part on the width of the web stabilizer, and the determinationthereof is within the skill in the art.

A remote mounted fan can be used as the source of negative pressure, orthe inlet of the supply fan in the web dryer that may be associated withthe assembly can be used as the suction source. A flex hose with adamper to control negative pressure can be attached to the vacuumreservoir via the hole 48.

In operation during a continuous web coating process, the device 10 isplaced next to a slot die coater 200, immediately upstream thereof, inthe direction opposite of web travel, as shown in FIG. 13A. The deviceis stationary and negative pressure is applied to the slot 25 (e.g.,negative pressure is applied to the body, through the vacuum reservoir16 or through a passage in shaft 12 a, such as with a fan or the like)to flatten the web and hold it down on the slot die coater 200positioned immediately downstream of the device 10. As the moving web100 travels over the leading highly polished surface 20A of the weblifter and stabilizer assembly 10, a static or frictional force iscreated that attracts the foil web 100 to the flat surface 20A of thedevice to assist in flattening the web along with the negative pressureslot 25. In a preferred embodiment, the negative pressure applied atslot 25 is typically in the range of −0.2 to −2 inches of water and maybe adjusted by means of a valve (not shown) in the vacuum line connectedto the suction source to obtain the desired degree of flattening whileminimizing the amount of frictional drag imparted on the moving web. Incertain embodiments, the device is positioned within 0.375 to 0.500inches of the slot die coater 200 discharge area, and slightly below thedischarge lips 201 of the slot die coater 200 to allow the web to wrapover the slot die coater for better contact and coating quality duringcoating. When a gap is desired in the coating on the web 100, the device10 is rotated about the longitudinal axis of the shaft stubs 12 (and 12a with alternate suction through shaft 12 a), such as from 1 to 3degrees depending on the process control, such as by actuating a shaftstub 12 with motor 17, to lift the web 100 off of the slot die coater200 (the Off Coat Position shown in FIG. 13B). In certain embodiments,the fan remains on at all times to maintain a constant negativepressure. After a predetermined amount of time (or web distance) toobtain the correct skip length, the servo motor 17 associated with thedevice 10 rotates the device 10 back down below the slot die coater 200to the On Coat Position. The cycle then repeats.

The ability of the web lifter/stabilizer device to guide and flatten atravelling web can be utilized in applications where web lifting is notrequired. In such applications, the device need not be rotatable.

FIG. 17 shows a representative embodiment of the fluid system andcontrol elements in accordance with certain embodiments. In thisembodiment, the system comprises a coating fluid reservoir 30, pump 40,bypass valve 63, supply valve 60, nozzle 70 and web lifter 15.Optionally, a fluid displacement mechanism 90′ is included toalternatingly draw and replace a small volume of fluid through conduit96. A controller 210 is incorporated into the system, which is able tocontrol the actions of the bypass valve 63, the supply valve 60, and weblifter/stabilizer 15. In some embodiments, which utilize a fluiddisplacement mechanism, the controller 210 controls the actions of fluiddisplacement actuator drive 91.

The controller 210 includes a processing unit which executes computerreadable instructions, adapted to perform the actions described below.The processing unit may be a general purpose computing device, such as amicroprocessor. Alternatively, it may be a specialized processingdevice, such as a programmable logic controller (PLC). The controller210 also contains a storage element, which is used to store theinstructions, as well as provide temporary storage for the processor'suse. The storage element may utilize any memory technology, such as RAM,ROM, EEPROM, Flash ROM, NVRAM, or any other suitable technology. Thecontroller 210 also includes an input device, such as a touchscreen,keyboard, or other suitable device. The input device is used to allowthe operator to input a set of parameters or a profile which should beused by the controller 210. This input device may also be referred to asa human machine interface or HMI. The controller 210 also has outputsadapted to control the valves and nozzle as described above. Theseoutputs may be analog or digital in nature, and may provide a binaryoutput (i.e. either on or off), or may provide a range of possibleoutputs, such as an analog signal or a multi-bit digital output. Usingthese outputs, the controller 210 is able to control the opening andclosing of bypass valve and supply valve 60, as well as the speed atwhich these operations occur. Similarly, it can control the movement ofthe web lifter 15, as well as the speed of that movement.

The valve actuators 51 and 61 driving valves 50 and 60, respectively,and fluid displacement actuator 91 driving chamber are preferablyservomotor drives having precise positioning capability at high travelspeed. Preferably, the actuators 51 and 61 are capable of driving theirrespective valves through the travel range from open to closed andclosed to open positions in less than 50 milliseconds. Similarly,actuator 91 is selected to expand volume chamber 90 in less than 50milliseconds and return to the compressed position in less thanmilliseconds. Web lifter/stabilizer 15 is positioned by actuator 73,preferably a servomotor having high speed positioning capability tocomplete the full cycle from on-coat position to the off-coat positionand from off-coat position back to web coating-on position in less than50 milliseconds.

To establish a profile of the thickness of one or more coated patches tobe applied along a length of a sheet comprising a continuous web in thedirection of web travel, the operator may enter the position on thesheet referenced to a starting position, and additional referencepositions defined in terms of web travel distance for control ofactuation of the various valves 50, 60 and lifter/stabilizer 15. Thesereference positions are initially determined from the desired lengths ofcoated and uncoated areas to be applied to the web to produce one ormore coated patches of precise dimension along the direction of webmovement with intervening segments of uncoated web having a secondprecise dimension along said web movement direction. These referenceposition parameters may also be adjusted depending on various criteria,such as the fluid rheology, and slot die setup.

The following describes an example in which the operator sets theparameters to produce coated patches of a precise desired length.Referring to the supply valve 60, the operator may provide the “positionat which the valve opens”, “position at which the valve closes”, or anintermediate “open” and “closed” positions wherein the valve ispartially open or partially closed. In some embodiments, the operatormay supply a set of positions and a corresponding indication of thestate of the valve, such as 20% open, 40% open, etc. In someembodiments, the opening and closing of the valve 60 may follow a custommathematical curve. For example, the mathematical curve may be a linearramp, an exponential function, a step function, or a parabolic function,or any combination of the previous. Similar parameters may be used forthe bypass valve 63. In one embodiment, profiles are determined througha working knowledge of the coating being applied and by generating acorresponding timing diagram. The valve timing and open/close profilesare then refined through experimentation.

The movement of the lifter/stabilizer 15 can also be controlled by thecontroller 210. In some embodiments, the lifter 15 is rotated by anactuator 73 to displace the web from the lips 72 of nozzle 70. Theoperator may enter a reference position when the lifter/stabilizer 15starts moving away from the lips 72. The operator may also enter areference position when the lifter/stabilizer moves toward the die lips.Subsequently, the speed of movement is automatically adjusted based onthe line speed and web position relative to the slot die. As above, agraph of the position of lifter 15 vs. sheet position may be a simplelinear ramp, an exponential function, or a parabolic function. Thisgraph determines the speed of movement of the lifter 15. In someembodiments, the operator may supply a set of reference positions and acorresponding indication of the state of the lifter, such as 20% awayfrom the die lips, 40% away from the die lips, etc.

Similarly, the movement of the optional fluid displacement mechanism 90′may be likewise programmed and controlled.

It is likely that certain combinations of parameters for the valves 50,60, web lifter 15 and fluid displacement mechanism 90′ will be utilizedfrequently. Therefore, in lieu of entering all of the parameters foreach component separately, the operator may create a “recipe”, which isa predefined set of parameters which describe the operation of all ofthe components. At a later time, the operator can simply enter the nameof the recipe, which conveys all of the associated details movementinformation to the processing unit. In some embodiments, the details ofeach recipe are stored in the storage element in the controller 210. Forexample, a “recipe” may be stored that generates the coating patternshown in FIG. 19, while a second “recipe” generates the coating patternshown in FIG. 21. In addition, the recipe may be stored locally andcontrol only the coated patch profiles, or it may be stored remotely aspart of a larger global recipe that stores other variable conditionssuch as line speed, web tension, dryer settings, and settings for otherequipment that is integrated to the coating line.

Using this controller, the operating characteristics of the variouscomponents can be programmed to create a wide range of coating profiles.For example, FIG. 18 shows the operation of the bypass valve 63, thesupply valve 60, and the web lifter 15 which can be used to create theprofile shown in FIG. 16. The horizontal axis represents distance on thesheet. This profile assumes that the coating is applied for 200 mm, andthen is not applied for 30 mm. This pattern is then repeated. Theembodiments disclosed herein are not limited to this pattern. Indeed,the coated and uncoated portions can be as small as 1 mm and can bearbitrarily large.

The following embodiments utilize the reference position of the sheetalong the direction of web travel to determine the actions of thevarious components. The position of the substrate materials is trackedby a high resolution encoder 220 attached to a roller shaft. In anotherembodiment, the encoder is coupled to a drive motor that represents webmovement. Upon initial start of the coating operation, the length of webtravel in relation to the location of die lips 72 is computed fromencoder information and translated into terms of web reference position.The signals from encoder 220 are in communication via a data bus to theservo drive controls of servomotors 51, 61, 73 and 91 to carry out therespective positioning actions of valves 50, 60, web lifter 15 and fluiddisplacement chamber 90, respectively. As is known to those skilled inthe knowledge of application of servo drives, these positioning actionsmay be carried out at very high speed with excellent precision accordingto mathematically programmed cam action profiles defined by the user.Positioning actions of two or more actuators may be coordinated toobtain precise control of the patch location and coating thicknessprofile and are represented as timing diagrams.

FIG. 18 shows an example timing diagram wherein at reference position199.5 mm, the bypass valve 63 begins to open, while the supply valve 60begins to close. This operation is completed by reference position 200mm, therefore the transition between the coating region and the uncoatedregion is very abrupt. This rapid transition tends to leave excessivecoating in the nozzle 70, which is unevenly applied when the supplyvalve 60 next opens at time 230 (see FIG. 16). While the valves 50, 60are being actuated, the web lifter 15 is moved from its on-coat positionto an off-coat position, away from the die lips 72. This movement beginsat reference position 199.5 mm and ends at reference position 200 mm.The coating is again applied at reference position 230 mm. Inpreparation for this application, the bypass valve 63 begins to close atreference position 229.5 mm. The bypass valve 63 is closed by referenceposition 230 mm. The supply valve 60 executes a similar profile goingfrom the closed state to the open state beginning at position 229.5 mmand ending at position 230 mm. The web lifter is also moved into theon-coat position as well. This movement begins at reference position229.5 mm and is completed by reference position 230 mm.

It should be noted that while the examples presented herein demonstratethe supply valve 60 and the bypass valve 63 operating in concert, thisis not a requirement. In other words, these valves 50, 60 are separateand their actuation may be controlled separately. In another embodiment,a three way valve may be employed, in which case, the actuation of thesevalves would be dependent on each other.

In some embodiments, particularly at higher coating speeds exceeding 5meters per minute, a fluid displacement mechanism 90′ is preferably usedas shown in FIG. 17. In these embodiments, the fluid displacementmechanism 90′ may be a chamber 90 having a changeable volume and asingle fluid connection 96, such that when the volume increases,material is drawn away from the nozzle lips 72 into cavity 71, throughconduit 96 and into the chamber. Conversely, when the volume decreases,material in the chamber 90 is forced back through conduit 96 into thenozzle cavity 71 and into nozzle lips 72 and is applied to the sheet. Inthe profile shown in FIG. 18, the fluid displacement chamber 90 of FIG.17 is preferably driven by a linear actuator 91 which begins to expandthe volume of chamber 90 at reference position 199.5 mm and is fullyexpanded by reference position 200 mm. When the material is to beapplied again, the fluid displacement chamber 90 is decreased in volumeby actuator 91 at reference position 229.5 mm. This chamber contractionis complete at reference position 230 mm.

Referring to FIG. 23, the fluid displacement mechanism 90′ may becomprised of a sealed bellows or diaphragm element to form chamber 90which is attached to stationary frame 97 which supports both the chamber90 and actuator 91. Actuator 91 is mechanically connected to thediaphragm element of chamber 90 by a mechanical coupling 92 to move theposition of the diaphragm inward to chamber 90 to reduce the internalvolume, or outward from chamber 90 to increase the internal volume.Fluid conduit 96 is in fluid communication with the internal volume ofchamber 90 and is also in fluid communication with the fluid system ofFIG. 17. Prior to operation, the chamber 90 and conduit 96 are filledwith coating fluid, coating solvent, or other suitable fluid media toprime the fluid displacement mechanism. In operation, the actuationdistance “Y” is controlled by actuator 91 in accordance with theinstructions from controller 210 of FIG. 17. In order to allow fastactuation of the fluid displacement action, the design of the diaphragmelement of chamber 90 is to be made with consideration of minimizing theactuation distance while obtaining the desired change in internal volumein the expanded state versus the volume in the contracted state. Traveldistance is preferably less than 6 mm for a response speed less than 50milliseconds. The diaphragm may be selected from commonly availableelastomeric materials, optionally reinforced with fabric strands, andsealed to a rigid shell or bowl to form the variable volume chamber 90.In a preferred embodiment, the volume chamber is constructed as a metalbellows of corrosion and solvent resistant material such as T304stainless steel. A single bellows type is preferred for effectivepriming of the chamber to avoid inclusion of air bubbles duringoperation. The forgoing descriptions of the variable volume chamber 90are meant to be exemplary as numerous designs of bellows and diaphragmelements are known to those skilled in the art and may be applied tomeet the requirements for minimal actuation distance, fast speed, andvolume displacement.

It is to be appreciated that the coating fluid contained in chamber 90,conduit 95, cavity 71 and die lips 72 undergoes a reversal in flowdirection for each actuation by actuator 91 such that fluid istemporarily displaced from the exit of die lips 72 into the die cavity71 and into fluid displacement chamber 90 when expanded and thenreturned via the same path to the die lips 72 when the chamber 90 iscompressed. Therefore, coating fluid is not withdrawn from the processto accommodate the control of the deposition of fluid on the web to makediscrete coated patches of precise dimension.

Of course, other coating profiles may be desired. FIG. 19 shows acoating profile where the leading edge 540 is much more even than thatof FIG. 16. Trailing edge 545 is also more even and abrupt. To createthis profile, the timing and speed of the various components is modifiedfrom that explained in conjunction with FIG. 18. A representative timingdiagram that may be used to create this coating profile is shown in FIG.20.

In this profile, the supply valve 60 and bypass valve 63 are controlledso as to begin closing earlier. In this profile, these valves 50, 60begin transitioning by reference position 195 mm and are completelytransitioned by reference position 196 mm. The web lifter 15 is notmoved until reference position 199.5 mm, and is quickly moved away fromthe die lips 72. When the coating is to be applied again, the valvesbegin transitioning by reference position 228 mm and are completelytransitioned by reference position 229.5 mm. The web lifter 15 is movedtoward the die lips 15, starting at reference position 229 mm and iscompleted by reference position 230 mm. In those embodiments where afluid displacement mechanism 90′ is utilized, the fluid displacementchamber 90 begins to expand at reference position 199 mm and is fullyexpanded by position 200 mm. Before the coating is applied again atposition 230 mm, the fluid displacement chamber 90 begins to contract atreference position 229 mm. Its contraction is completed at referenceposition 230 mm.

FIG. 21 shows another coating profile that can be created usingembodiments disclosed herein. In this embodiment, the leading edge 562is ramped to its maximum value. Similarly, the trailing 565 is tapered,rather than abrupt. FIG. 22 shows a timing diagram that may be used tocreate this profile. In this embodiment, the valves 50, 60 open andclose more slowly, so as to create the tapered leading edge 562 andtrailing edge 565.

It should be noted that the representative timing diagrams describedherein are not the only timing diagrams that can be used to create thedesired coating profiles. In addition, other coating profiles arepossible and can be created by varying the operation of the valves,nozzle and fluid displacement mechanism.

The use of a controller to control the actuation of the valves 50, 60and the movement of the web lifter 15 may allow the elimination of afluid displacement mechanism 90′, particularly at coating speeds below 5meters per minute. For example, by precisely controlling the positionand the speed at which the valves turn on and off, the amount of excesscoating that remains in the nozzle 70 can be reduced.

In the examples above, the system is programmed by referencing allactuations to position. In another words, the system receives inputwherein an absolute position and a desired action are presentedtogether. However, other points of references may be used to indicatewhen an action should take place. For example, the actions of the valves50, 60 and the web lifter 15 may be referenced to the turn-on andturn-off positions. For example, the user may specify that the coatingshould be applied for 200 mm, followed by a 30 mm uncoated region. Theactuation of the valves 50, 60 may be input as relative offsets fromthese turn-on and turn-off positions. Referring to FIG. 20, the valveswould be programmed to being transitioning at position offset −6 mm (200mm-194 mm), and would complete this transition at position offset −4 mm.Similarly, the next transition of the valves would be referenced to theturn-on position (230 mm). This method of conveying information to thecontroller may be extremely valuable, as it allows the same coatingprofiles to be used with different length regions, by simply modifyingthe turn-on and turn-off locations, without modification to the otherparameters.

Another advantage of the position based reference system describedherein is that the controller may automatically compensate for changesin coating speed. For example, if the speed of the roller 315 ischanged, the controller can determine that the times associated witheach actuation are different and can compensate for this change andgenerate the same coating profile as was done previously.

The controller can also be used to apply a coating to the opposite sideof a previously coated sheet as well. In a preferred embodiment shown inFIG. 17, a web 310 is coated on a first side by a first coating nozzle70 a having a fluid delivery system 301 a and web lifter 15 a operatingas previously described to coat patches of a desired length, spacing andthickness profile in the direction of web travel. The web path is thenre-directed by rollers 314 and 315 by turning on the uncoated side ofthe web in order to present the web in the preferred orientation at asecond coating nozzle 70. The second side of the web 310 is then coatedas previously described. In some embodiments, it is imperative that thecoating patches on the first side are exactly aligned with those createdon the opposite side. In other embodiments, it may be desirable toadvance or delay the application of coating relative to the pattern onthe first side. Using the input device, the operator can program theregistration of the opposite side. In some embodiments, this is achievedby programming the start and stop positions to have a certainrelationship to the previously applied coatings on the first side. Inother embodiments, the operator enters the desired offset (i.e. 0indicates alignment, positive values indicate a delay and negativevalues indicate an advancement). In this embodiment, the system maycontain a vision system 230 as shown in FIG. 17 positioned to view thepreviously coated patches and capable of detecting the transitionbetween an uncoated region and a coated region. Once this web positionpoint is determined, the controller can use the speed of the roller 15as computed from the signal of encoder 220 or a suitable roller driveinformation signal to determine the time at which coating should beapplied to the second side. The vision system 230 may be comprised of acontrast sensor in data communication with controller 210 and with servodrives controlling actuators 51, 61, 71 and 91. A number of such visionsystems are available in the industrial controls and sensors market andmay be selected to provide fast response speed in order to report thedetected transitions from coated to uncoated locations on the moving weband from uncoated to coated locations in order to effect timely actionby controller 210 and the servo drives controlling servomotors 51, 61,71, and 91. Response time for the contrast sensor device is preferablyless than 100 microseconds. In embodiments including the vision systemfor registration of patches, the controller 210 must be capable ofprocessing all mathematical operations to initiate the actuator anddrive motor actions at a frequency at least 2 times the rate at whichthe desired coated patch sequences (coated and uncoated lengths) arepassing by the sensor 230.

Another, more preferred type of registration controller not only sensesthe edge of the coating patch before it arrives at the coating head foralignment of the coating patches, but also has a second set of sensors231 and 232 that measure the alignment of the two coated patches andcompares the measured value against the target value and automaticallyapplies a correction to the registration distance of the subsequentcoated patch. This type of system provides for more robust operation byproviding both feed-forward and feed-back control of the coatingregistration process and can automatically compensate for the time lagsassociated with communication delays among the various control systemsused in the entire coating device. Furthermore, this preferred type ofregistration system improves the production yield by reducing the numberof defects caused during changes in the coating line speed, or tensionchanges due to splices, for example.

Another benefit from the preferred coating registration method is thatthe coating patches are automatically measured and the measurement datacan subsequently be recorded into a data logging system for statisticalanalysis and quality control.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. A method of applying a coating to a web using asystem comprising a supply valve, a bypass valve, a nozzle, a web lifterand a controller to control said supply valve, said bypass valve andsaid nozzle, said method comprising: inputting to said controller thereference positions on said web where said supply valve is to open andclose; inputting to said controller the reference positions on said webwhere said bypass valve is to open and close; inputting to saidcontroller the reference positions on said web where said web lifter isto be actuated to move said web toward and way from said nozzle; movingsaid web past said nozzle; tracking the position of said web; and usingsaid controller to control said supply valve, said bypass valve, saidnozzle and said web lifter based on said inputted reference positions todeposit said coating on said web.
 2. The method of claim 1, wherein saidcontroller comprises memory storage to store reference position data forsaid web.
 3. The method of claim 2, wherein said reference position datacomprises positions of said web where said supply valve is to open andclose.
 4. The method of claim 2, wherein said reference position datacomprises positions of said web where said bypass valve is to open andclose.
 5. The method of claim 2, wherein said reference position datacomprises positions of said web where said web lifter is to be actuatedto deflect said web.
 6. The method of claim 1, further comprisingsensing the position of said web and communicating the sensed positionto said controller.
 7. The method of claim 1, wherein said web lifter ispositioned upstream of said nozzle in the direction of travel of saidweb.
 8. The method of claim 1, wherein said web is a conductivesubstrate.
 9. The method of claim 1, wherein said actuation of said weblifter rotates said web lifter.
 10. The method of claim 1, wherein saidcontroller controls the opening and closing of said bypass valve and thespeed at which said bypass valve is opened and closed.
 11. The method ofclaim 1, wherein said controller controls the opening and closing ofsaid supply valve and the speed at which said supply valve is opened andclosed.
 12. The method of claim 1, wherein said web lifter has a bodyhaving a first portion defining a leading edge of said body, and asecond portion defining a trailing edge of said body, said first portionbeing spaced from said second portion so as to define an air entry slotbetween them for the entry of air upon application of negative pressureto said body.
 13. The method of claim 12, further comprising applyingnegative pressure to said air entry slot.